The present invention relates to power tools; more particularly the present invention relates to power tools in which a nose piece and drill bushing are utilized for guiding a drill bit through a drill fixture into a work piece.
In many drilling operations, particularly aircraft, it is well known to utilize drilling apparatus including a nose piece with a taper lock style drill bushing mounted at its outboard end. The taper lock style drill bushing is used to lock the drilling apparatus to a drill fixture which is then positioned over a work piece. Typically, the drill fixture is rigidly mounted to the work piece to assure accurate placement of the drilled hole. The drill fixture includes two fasteners which are used to lock the taper lock style drill bushing in position against the drill fixture. The taper lock style drill bushing is usually threaded into a nose piece at the end of a power drill and the nose piece is then rigidly attached to the power drill. Consequently, when the nose piece and taper lock style drill bushing are attached to the power drill, the power drill may be firmly affixed to the drill fixture thus allowing accurate drilling of a hole in the work piece.
A problem arises when the drilling apparatus has an appendage extending outwardly therefrom. Such appendage may contain operational controls, a power source, or speed reduction gearing. When it is necessary to rotate the entire drilling apparatus to position the taper lock style drill bushing with respect to the fasteners which extend from the drill fixture, the appendage extending from the drill may butt up against a bulk-head, a wall or a spar. Such problems frequently occur when the hole to be drilled is in a corner. This contact of the appendage with the bulk-head, wall or spar prevents the full rotation of the drilling apparatus thus preventing proper engagement of the taper lock style drill bushing with the fasteners which extend from the drill fixture. To solve this problem a system is required in which the nose piece may be rotatably positioned with respect to the rest of the drill apparatus while the drill apparatus is in position for drilling a hole. Ideally, such system should provide an infinite range of positions of the nose piece with respect to the rest of the drilling apparatus. Such system would allow the appendage extending from the drill to not interfere with the locking of the drilling apparatus to the drill fixture.